I don't see it that way. On my cameras if I set aperture and shutter speed manually, but allow my camera free access to choose the iso, it has complete automatic control of the brightness of my photos as they are produced by the processor in the camera and saved as jpegs.
In the scenario you describe, you're manually controlling exposure through f-stop and shutter speed. The camera is controlling JPEG lightness through its selection of ISO.
We agree here, except to clarify I'm controlling the amount of light that hits the sensor.
You're controlling the exposure. By definition, exposure is the light intensity from the scene per unit area of the sensor. This is determined by the amount of light in the scene, f-stop, and shutter speed.
Exposure times the area of the sensor yields the total amount of light delivered to the sensor.
And then the camera is controlling JPEG lightness through its selection of ISO. And what the camera is controlling is the lightness of the photo that results from its ISO decision. Which is the only place I can determine the exposure used to create the photo.
Whatever process you use to evaluate exposure, make a decision about whether or not it's to your liking, and determine which combination of changes to shutter speed or f-stop to make to optimize exposure, that doesn't change the fact that exposure is determined by scene brightness, f-stop and shutter speed. ISO has no direct affect.
I have no way of seeing the amount of light that hit the sensor. A photo must be created by the camera's processing for me to determine the exposure of my photo. And I really don't care how much light hits the sensor, I only care what the exposure as exhibited in the photo created by the camera looks like.
Your usage of the term, exposure, is not consistent with the meaning of the term. You use it to describe the lightness of a photo. That's not it's meaning in photography...hasn't been for many generations.
Of course, you're free to use language as you see fit. That said, if you continue using the term to mean something it isn't, other DPR members will continue to correct that usage.
Only if I want to post process my images would I have any manual control of the observed image brightness.
The exposure compensation (EC) setting you've chosen manages image lightness. A setting of 0 is generally a reflection of being satisfied with the camera's choice of ISO. Negative or positive EC settings will push ISO section lower or raise it higher, respectively.
Again we agree. EC only biases the calibration of the camera's metering system. I can choose to make things brighter or darker than default as dictated by the camera's inbuilt metering and processing, but EC cannot change the exposure itself.
Correct. EC influences exposure in a manner similar to how ISO influences exposure, it's impact on the camera's choice of the two exposure settings: f-stop and shutter speed.
However, you may have missed the point of my comment. You seemed to say that in manual plus auto-ISO, you have no ability to change image lightness. Was that your intent?
If so, EC allows you to manage the ISO used. You can also switch between different metering modes to exert influence on the camera's choice of ISO. It's not something that can be altered only in post.